There is a need to provide a simple and accurate method for field personnel in electric utilities to measure the dielectric fluid that may have leaked from underground high voltage transmission systems. Older underground transmissions systems that require dielectric fluid for cooling are manufactured in section lengths of approximately one thousand to two thousand feet. Special high voltage splices are used to join the sections together. Often these underground cable systems are buried under city streets and access to the splices are through manholes leading to underground containment vaults.
Containment vaults are large, typically ten feet wide by fifteen feet long by ten feet deep. Transmission systems of this type have sophisticated leak detection and upon being alerted to the possibility of a leak all the cable vaults are visually inspected by removal of the manhole covers in the street and looking into the vault to determine if there is an oil leak. Vaults typically contain rainwater and the presence of oil of any depth is difficult for field personnel to determine quickly. A sixteenth of an inch of oil/dielectric fluid looks the same as a foot. A wide variety of techniques are employed by utility technicians to determine the presence and level of oil within an enclosed vault. A wrong “guesstimate” could lead to costly site remediation where none may be required or worse, not initiating the proper response where it is required.
Many methods of measurement were researched for the purpose including level measurement floats designed to float in fluids with various specific gravities. Other electronic products used in geological applications were investigated as well. Both seem clumsy and or expensive. There is a need, therefore, for a measuring device that is simple to use, inexpensive to use and manufacture, and accurate in its measurement.